1. Technical Field of the Invention
The present invention relates to a process and apparatus for the production of pile-up lids, and to a pile-up lid obtained thereby.
2. Prior Art
Conventional lids are generally formed by a perimetric element, apt to be positioned on the outside edge of a container to be closed, and by an upper wall closing the perimetric element.
With regard to a particular structure of lid, generally circular in shape, of the kind, for example, that is used in the ice cream containers and the like, it is formed by a ring-shaped element at the top of which a disk is inserted to close the upper opening of the container, which disk has its circumference edge folded upwards, on which edge the upper edge of said ring-shaped element is in turn folded over and fixed. In this way a stable complex is formed.
Furthermore, in this type of lid, a ring-shaped bead is formed around the circumference of the surface of said ring-shaped element, said bead having the function of creating a snap-on engagement with the protruding edge of the associated container at its top.
However, these known lids have the disadvantage that they cannot be piled up one on top of another because, due to their shape, the diameters of the top and bottom edges of the lids are identical.
This entails a number of troubles during storage and transport, as said lids must be stored in large containers, generally plastic bags, and must be inserted into the inside thereof loose, with a consequent use of a great deal of space. Furthermore, when stored in this way they are subject to knocks, folding, breakage and generally, due to the possibility of free movement within the packing, to rubbing, which can result in deterioration of the surface appearance and flatness thereof.
Furthermore, the above conditions cause a number of troubles for the operator when taking up said lids from their packing for loading them, in pile, into the operating machine in order to carry out their insertion onto the relative containers, resulting in considerable loss of time.